High efficiency transmission grating for the ESO CUBES UV spectrograph

TL;DR

This paper presents the development and characterization of a high-efficiency transmission grating using microlithography for the UV spectrograph CUBES on the VLT, aiming for high resolution and efficiency.

Contribution

It introduces a novel microlithography-based fabrication process for transmission gratings tailored for the CUBES UV spectrograph, including design, prototyping, and performance evaluation.

Findings

Successful fabrication of high-resolution transmission gratings

Achieved optical performance meets spectrograph requirements

Outlook on final grating realization with advanced lithography techniques

Abstract

CUBES is the Cassegrain U-Band Efficient Spectrograph, a high-efficiency instrument operating in the UV spectral range between 300nm and 400nm with a resolution not less than 20000. CUBES is to be installed at a Cassegrain focus of the Very Large Telescope of the European Southern Observatory. The paper briefly reviews various types of devices used as dispersing elements in astronomical spectrographs to achieve high resolution, before identifying binary transmission gratings produced by microlithography as the best candidate technology for the CUBES instrument. We describe the lithographic fabrication technology in general, two different design considerations to achieve the required high-resolution transmission grating, its prototyping by a direct-write lithographic fabrication technology, and the characterization of the achieved optical performance. An outlook to the realization of the grating for the final instrument, taking the most recent developments of lithographic writing capabilities into consideration is given.